Method and apparatus for mixing fluids

ABSTRACT

A method for entraining and mixing gas with liquids within a conduit or drop structure, comprising the channeling of one or more liquid flows into spiral flows of predetermined radius (radii), reducing the predetermined radius (radii) to increase the centrifugal forces acting upon the spiral flow(s) as the spiral flow(s) enter the conduit, and allowing gas access to the conduit to mix with and entrain within the spiral flow within the conduit or drop structure. The method can facilitate the mixing of gas with one or more fluid flows and/or reduce the release of gas emissions from the fluid(s) into the surrounding environment.

This application claims the benefit of is a continuation-in-part of U.S.patent application Ser. No. 09/561,999 filed May 1, 2000, now U.S. Pat.No. 6,419,843 B2 which claimed the benefit of provisional patentapplication No. 60/135,476 filed May 24, 1999.

FIELD OF USE

The invention relates generally to applications whereby it is desirousto introduce or reintroduce gas with liquid flowing through pipes,and/or mix two fluids within a pipe. In particular, this method can beused, but is not so limited, to mix and entrain air and other odorousgas emissions into sewage to reduce odorous gas emissions and to reducehydrogen sulfide corrosion and abrasive wear in waste water conveyance,collection and treatment systems.

BACKGROUND OF THE INVENTION

Throughout past decades, sewers have been utilized to efficientlytransport waste water or sewage from locations where it was generated towaste water treatment plants and other destinations. These sewersconsist generally of pipelines locate below ground level and orientedwith a slight downward grade in the direction of the sewage flow.Gravity acts upon the sewage to cause it to flow within the pipelinestoward its ultimate destination. These pipelines are sometimesinterconnected by “drop structures” that allow the sewage to flow fromone line into the drop structure, drop vertically therewithin, and thento flow out of the drop structure into additional pipes or otherstructures.

One problem that occurs during the transport of sewage is the release ofsulfides from the sewage. Sulfides form as a result of bacterialreduction of sulfates within the sewage in an anaerobic environment. Assewage ages, the level of sulfides increases. Drop structures within asewer system can provide a beneficial aeration of the sewage flow byintroducing additional dissolved oxygen into the flow. The dissolvedoxygen reacts with the sulfides, resulting in less chemical volatilityin the sewage. This aeration is particularly beneficial where the sewageis fresh and contains a relatively small amount of dissolved sulfides,such as hydrogen sulfide (H₂S).

Unfortunately, in most practical applications, sewage contains asignificant amount of potentially volatile dissolved molecular hydrogensulfide gas. Turbulence within the sewage flow can cause this dissolvedgas to be released into the surrounding air. Significant sources ofturbulence in sewage flow, and hence the emission of hydrogen sulfidegas in a sewer, occur in drop structures such as interceptor dropmaintenance holes, joint structures, forcemain discharges and wet welldrops in sewer pumping stations. Thus, while drop structures canreintroduce dissolved oxygen into the sewage flow, lowering the level ofhydrogen sulfide gas, they can also cause the release of hydrogensulfide gas. The hydrogen sulfide emissions often cause corrosion withthe drop structures and adjacent sewer lines, and cause odor problemseven the most elegant, pristine neighborhoods.

One known type of drop structure comprises an influent line, amaintenance hole and an effluent line. The influent line runs almosthorizontally at a relatively shallow depth below the ground surface inthe form of a pipe. The maintenance hole is located below the streetlevel maintenance hole manhole cover. The maintenance hole is generallycylindrical in shape with a vertical longitudinal axis. The effluentline is another almost horizontal pipe that exits slightly above thebottom of the maintenance hole. Turbulent waste water flow is createdwhen the sewage, which has a substantial amount of potential energy,exits from the influent line near the top of the maintenance hole andtumbles down like a waterfall to the side wall and base of themaintenance hole. Then the sewage pools and eventually flows out theeffluent line. This turbulent action releases hydrogen sulfide gas intothe air. To reduce the problem of gas release, while still allowingbeneficial aeration of the sewage, the potential and kinetic energy inthe sewage must be dissipated.

One known method is to create a wall hugging spiral flow down themaintenance hole to dissipate the energy by friction. The spiral flow isgenerated by the insertion of a vortex form connected to the influentline near the top of the maintenance hole. The vortex form is generallyhelical in shape and is placed directly below the manhole cover near thetop of the maintenance hole. The vortex form channels and diverts theflow from its languid state into a spiral flow descending down thecylindrical wall of the maintenance hole. The vortex form can be made ofconcrete with applied protective coating, or made of a noncorrosivematerial, metal or plastic, such as PVC, High Density Polyethylene(HDPE) or other like materials. The vortex form may be manufactured atthe factory or on-site.

Two problems remain to be solved when applying this known method ofusing a vortex form in a drop structure for sewage flows. First, theupstream flow velocities within the influent line are usually not largeenough to create a stable spiral flow on the vertical wall of a typicalmaintenance hole. Thus, the flow, rather than continuing to spiral downthe cylindrical wall of the maintenance hole, will generally revert to aturbulent descending flow similar to waterfall, losing the effectiveenergy dissipation of the spiral flow and releasing significant amountsof hydrogen sulfide gas into the air. Second, quite often themaintenance hole is used for additional lateral influent connections atelevations lower than the main influent pipe. Consequently, the lateralinfluent connections disrupt the spiral flow and create a turbulentwaterfall of sewage to the bottom of the maintenance hole, againreleasing significant amounts of hydrogen sulfide gas into the air. Theadditional influent pipe may run in any direction, but at a lower depththan the main influent pipe.

SUMMARY OF INVENTION

It, therefore, is an object of this invention to provide a method forreducing gas emissions of a fluid through the entraining and mixing ofgas with the liquid.

It is also an object of this invention to provide a method for mixinggas with one or more fluids in a conduit.

Another object of this invention is to provide a method for use in sewerdrop structures that significantly reduces odorous gas emissions fromthe sewer.

A further object of the invention is to reduce hydrogen sulfidecorrosion in waste water conveyance, collection and treatment systems.

A benefit of this invention is the improved way in which the methodhelps to protect conveyance or collection systems from abrasive wear.

Another benefit is the way the invention in particular improves thequality of wastewater by wastewater aeration.

The foregoing objects and benefits of the present invention are providedby a method for reducing gas emission and for entraining and mixing gaswith liquids. The method comprises channeling a fluid flow though one ormore pipes, introducing the flow from the pipe(s) into a conduit orchamber through the use of spiral flows of predetermined radii, reducingsuch radii to increase centrifugal forces acting upon the flow,introducing gas into the reduced radius flow and continuing the reducedradius flow within the conduit until the gas is substantially entrainedwithin the flow. This method can be implemented through the use of amaintenance hole and an influent line for carrying liquid to themaintenance hole, a vortex form which accepts the liquid from theinfluent line, the vortex form comprising a spiral channel of decreasingradius disposed substantially within the maintenance hole, and a conduitalso disposed within the maintenance hole and fluidly connected to thevortex form and extending substantially downwardly from the vortex formto a flow exit near the maintenance hole base. The fluid flowing fromthe influent line enters the vortex form and is channeled by the vortexform into a spiral flow with a radius smaller than the maintenance holewall radius. The reduction in the radius of the channel outer wallcauses the centrifugal forces acting upon the fluid flow to increase,forcing the flow to continue in intimate contact with the outer wall ofthe channel. The fluid then flows from the reduced radius of the vortexchannel into the conduit and, aided by gravity and the flow's acquiredrotational velocity, continues its spiral descent towards themaintenance hole base, in substantially intimate contact with theconduit wall. The spiral flow then exits the conduit near themaintenance hole base into an energy dissipating pool.

The method creates an accelerated fluid flow sufficient to createsubstantial intimate contact with the vortex form and conduit wallthroughout the fluid flow's descent in the maintenance hole. Thisintimate contact creates frictional forces that reduce the kineticenergy of the flow and inhibit turbulent flow. The reduction inturbulent flow in turn reduces the release of gases, including hydrogensulfide. In addition, the spiral flow in the conduit creates an air corewith reduced pressure in the center of the conduit, inhibiting theescape of any hydrogen sulfide gas into the environment and encouragingthe reintroduction of any escaped gas back into the spiral flow and theenergy dissipating pool.

In another embodiment of the invention, two influent lines may be usedto channel the same or separate flows into the same conduit at twodifferent but proximate locations. The influent lines can originate froma single line or from two distinct lines and may contain the same ordifferent fluids. The flows are then introduced into the conduit throughreducing-radius vortices in opposing rotational direction.

In certain embodiments of the invention, it may be advantageous toutilize a vortex form channel with a downwardly sloping base sufficientto create an accelerating spiral flow. The method may also utilize avortex form incorporating an entrance flume designed to accept the fluidflow from the influent line and more gently direct the flow into thevortex channel. This entrance flume may also incorporate a slope tocreate an accelerating flow into the vortex channel.

The invention also contemplates utilizing in certain applications of theinvention various conduit base configurations for allowing the fluidflow to exit the conduit into the energy dissipating pool. These flowexit paths vary based on the desired fluid flow rates, the energydissipating pool depth, and the existence and configuration of anyeffluent lines running from the conduit.

While this invention is particular useful in wastewater conveyancesystems, it is not so limited, and can be applied to any system whereone desires to mix and entrain one or more gases, including air, intoone or more fluid flows within a conduit. Additional applications forthe present invention include aeration and/or purification of water inwastewater treatment plants, fishery basins, and natural streams, lakesand bays, and heat transfer in power plant cooling basins. Thisinvention may also be applied to mix food and beverage liquids; to mixconstituents in pharmaceutical applications, including applications tosuspensions and emulsions; and to mix construction materials includinginsulation materials, fillers, and high-air concentration mortars andconcrete. Thus, the particular embodiments discussed below are notexhaustive and are not intended to limit the scope of this invention.

BRIEF DESCRIPTION

Other objects, features, and advantages of the present invention willbecome more fully apparent from the following detailed description ofcertain embodiments, the appended claims, and the accompanying drawingsin which:

FIG. 1 is a side elevation, cross-sectional, view of one embodiment ofthe present invention with a portal-type flow exit;

FIG. 2 is the cross-sectional view A—A of the embodiment illustrated inFIG. 1;

FIG. 3 is perspective view of another embodiment of the presentinvention with a flow exit comprising a plurality of legs;

FIG. 4 is a side elevation view of an additional embodiment of thepresent invention with a suspended flow exit;

FIG. 5 is a top plan view of a portion of an influent line and a vortexform;

FIG. 6 is a perspective view of one embodiment of the vortex form;

FIG. 7 is a perspective view of another embodiment of the presentinvention using two vortex forms from a single influent line;

FIG. 8 is a perspective view of another embodiment of the presentinvention using two vortex forms from two influent lines.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates in a side elevation view one embodiment of a sewerapparatus 10 constructed in accordance with the present invention.Referring to FIG. 1, the sewer apparatus 10 includes an influent line12, a vortex form 20, a maintenance hole 30, a conduit 40, a flow exit50, and an effluent line 60.

The maintenance hole 30 in which the vortex form 20 is disposed may beidentified from street level as being below a manhole cover 32. FIG. 1shows the maintenance hole 30 as being cylindrical in shape and orientedvertically. A lateral line 33 for inputting additional city sewerflowage into the maintenance hole 30 may be disposed below the influentline 12. The base 34 and walls 36 of the maintenance hole 30 aregenerally concrete. An energy dissipating pool 72, comprised of sewage,forms at the base 34 of the maintenance hole 30. An effluent line 60 isconnected to the maintenance hole 30 near the top level of the energydissipating pool 72.

As illustrated in FIG. 1, sewage flows from the influent line 12 intothe vortex form 20 near the top of a maintenance hole 30. The influentline 12 is generally a cylindrical pipe running slightly below theground surface. To create an accelerated flow of sewage, a portion ofthe influent line 12 can be set at a predetermined downward slopingorientation. Such an orientation is shown in FIG. 3. The slope necessaryto create a constant or accelerating velocity is known as the criticalor supercritical slope, respectively. A critical slope in which thevelocity of the sewage flow would remain constant is identified ashaving a Froude Number (Fr) equal to one. A supercritical slope in whichthe sewage flow is accelerating is identified as having a Froude Numbergreater than one (Fr>1). The Froude Number is calculated using theformula Fr=V/(g*d)½, where V represents average sewage flow velocity, drepresents flow depth and g represents acceleration due to gravity,approximately 32.2 feet per second squared. Each of these factors caneffect the critical slope of the influent line 12. While the criticalslope will generally occur around one to three percent, it is envisionedthat the desired slope could vary anywhere from one percent or more. Inthe embodiment illustrated in FIG. 3, the influent line 12 descends at asupercritical slope of about ten percent slope to create an acceleratedflow.

Referring again to FIG. 1, the influent line 12 connects to the vortexform 20 and maintenance hole 30 near the top of the maintenance hole 30.The vortex form 20 is disposed within the maintenance hole 30 forreceiving the sewage from the influent line 12 and is generally shapedto create a descending spiral flow. FIG. 12 presents the cross-sectionalview A—A of FIG. 1, illustrating the vortex form in further detail.Referring to FIG. 2, the vortex form 20 includes a vortex channel 24,and may in certain embodiments also include an entrance flume 22. In theembodiment of the present invention shown in FIG. 1, the entrance flume22 is fluidly connected to the influent line 12. The entrance flume 22can take any shape capable of transporting the sewage from the influentline 12 to the vortex channel 24. In the embodiment illistrated in FIG.1, the entrance flume 22 consists of a base 21 and side walls 23. Thevortex channel 24 is fluidly connected to the entrance flume 22 andcomprises a base 25, an outer wall 26, and an inner wall 27. While thespecific vortex channel shown utilizes a flat base 25 with substantiallyvertical side walls 26 and 27, it is envisioned that these structurescould take on any shape capable of transporting the sewage in a spiralflow.

The vortex form 20 may be made of concrete with applied protectivecoating, or made of a noncorrosive material, metal or plastic, such asPVC, High Density Polyethylene (HDPE) or other like materials. Thevortex form 20 may be made in advance at the factory or on-site. Asshown in FIGS. 3 and 4, the entrance flume 22 and/or vortex channel 24may be manufactured and oriented with their bases having a supercriticalslope, allowing the sewage to accelerate as it flows through the vortexform 20. The selected slopes of the influent line 12, the entrance flumebase 21, the vortex channel base 25 will not necessarily be the same. Inthe embodiment illustrated in FIG. 1, the influent line 12 issubstantially horizontal, while the entrance flume base 21 and thevortex channel base 25 have a supercritical slope of about ten percent.

As noted, while the embodiment shown in FIGS. 1 and 2 illustrate avortex form containing an entrance flume 22, other embodiments of thepresent invention may fluidly connect the vortex channel 24 directly tothe influent line 12, omitting the use of the entrance flume 22.Examples of such embodiments are shown in FIGS. 3, 4, and 5.

Referring to FIG. 2, the vortex channel 24 directs the sewage flow intoa substantially spiral flow. The vortex channel 24 also reduces theradius of this spiral flow in order to increase the centripetal forcesacting upon the flow. This is accomplished through the reduction inradius of the outer wall 26, which will increase the centripetal forcesapplied by the outer wall 26 on the spiral flow. In the embodiment shownin FIG. 2, a radius transition section 28 supports the outer wall 26 andreduces the radius of the spiral flow created by the vortex channel 24(shown in FIG. 2 as R1) to the radius of the conduit 40 (shown as R2).The radius transition section 28 also aids in directing the flow fromthe vortex channel 24 into the conduit 40. The radius transition section28 is generally made of a noncorrosive metal or plastic with concrete ora foam fill material.

To allow the sewage flow to enter the conduit 40, inner wall 27 mustinclude a height transition section 29 (identified on FIGS. 2, 4, and 6as section A-B) which allows the sewage flow to enter the conduit 40. Itis envisioned that this transition section could take many forms,including a sharp vertical cut or a gradual decrease in wall height. Ithas been found to be advantageous, however, to fabricate inner wall 27such that its height profile reflects an axial flow velocitydistribution. This type of cut is illustrated in FIG. 6.

Referring again to FIG. 1, conduit 40 is disposed within maintenancehole 30 and fluidly connected to vortex channel 24. Conduit 40 comprisesa pipe wall 45 having a radius smaller than maintenance hole 30 andextending substantially downwardly from vortex form 20. Conduit 40further comprises a base 46, and a flow exit path 50 near saidmaintenance hole base. The upper portion of the pipe wall 45 may beconstructed integrally with inner wall 27.

Still referring to FIG. 1, the sewage spirals and falls from vortexchannel 24 into conduit 40, along the inner surface 47 of pipe wall 45.This flow continues to descend along the inner surface 47 of pipe wall45 in a substantially spiral fashion until the sewage nears the conduitbase 46. The conduit base 46 is disposed below the surface of the energydissipating pool 72 and at or above the base 34 of the maintenance hole30 to create a flow exit path 50. The sewage flow accumulates in theconduit base where it eventually flows through the flow exit path 50,located at or near the conduit base 46, into the energy dissipating pool72 near the bottom of the maintenance hole 30.

The flow exit path 50 may comprise any structure that allows the sewageflow to exit the conduit 40 at a predetermined flow rate. One example ofa flow exit path is shown in FIG. 1, comprising a portal 56 in theconduit base 46. The portal 56 allows the sewage flow that hasaccumulated in the conduit base 46 to exit into the energy dissipatingpool 72. Additional embodiments of the flow exit path 50 are shown inFIGS. 3 and 4. In FIG. 3, the flow exit path 50 comprises a plurality oflegs 52 connected to and supporting the conduit base 46. The pluralityof legs 52 are themselves supported by the maintenance hole base 34. Theplurality of legs 52 allows the sewage flow within the conduit base 46to be fluidly connected to the energy dissipating pool 72 and allows thesewage flow to exit the conduit base 46 at a predetermined flow rate. InFIG. 4, the flow exit path 50 comprises a suspended conduit support 80.The suspended conduit support 80 includes a conduit anchor 82 and avortex form base support 84. The vortex form base support 84 isconnected to both the maintenance hole side wall 36 and the maintenancehole base 34, and supports the vortex form 20 and conduit 40 in asuspended fashion. The conduit anchor 82, comprising a rigid structurecapable of securing the conduit 40, is connected to the maintenance holeside wall 36 and provides horizontal support for the conduit 40. Theconduit support 80 allows the conduit 40 to be suspended above themaintenance hole base 34, thus allowing the sewage flow to exit theconduit 40 at the conduit base 46 and enter the energy dissipating pool72.

Once the flow has reached the energy dissipating pool 72, it may bedrawn away for further transport though an effluent line 60, as shown inFIG. 1. In another embodiment, shown in FIG. 4, the sewage flow may bedrawn into a treatment pool 62 for further treatment.

As illustrated in FIG. 3, the present invention may utilize an airrelief 70 to equalize substantially the air pressure within themaintenance hole 30 above the vortex form 20 with the air pressurewithin the maintenance hole 30 below the vortex form 20 and within theeffluent line 60. Air relief 70 comprises a pipe connecting the topportion of the effluent line 60 with the maintenance hole 30 above thevortex form 20. The air relief 70 substantially equalizes the airpressures in the upper influent line 12 and the lower effluent line 60,drawing the air from the higher pressure influent line 12 downward tothe lower pressure effluent line 60. This pressure equalization, bydrawing the air through the air relief 70 into the effluent line 60,further prevents the leakage of noxious gases not absorbed by the sewageflow within the maintenance hole 30. These gases, dragged by theinfluent flow and not consumed by the spiral flow, would otherwise riseand emit from the improved sewer apparatus into the neighborhood. Asillustrated in FIG. 5, in another embodiment the air relief 70 comprisesa pipe extending through the vortex form, providing a path for the airto travel from the higher pressure area above the vortex form 20 to thelower pressure area below the vortex form 20. The air relief 70 of thisembodiment acts in the same fashion as the previously describedembodiment to prevent the leakage of noxious gases not absorbed by thesewage flow within the maintenance hole 30.

Referring to the embodiment illustrated in FIG. 1, in operation,incoming sewage at a small slope enters the vortex form 20 at theentrance flume 22 and descends through the vortex channel 24. Thesupercritical slope of the entrance flume 22 and the vortex channel 24provides rising flow velocities with a partial potential energytransition into kinetic energy. Even though sewage flow encounters anarrowing of the cross-section of the entrance flume 22, the water levelgenerally does not rise due to the flow acceleration created by thesupercritical slope of the base 21. The flow is then directed within thevortex channel 24 by the radius transition section 28 and the heightreduction section 29 of the inner wall 27 into a smaller radius conduit40.

The sewage flow then spirals downwardly against the inside wall of theconduit 40, creating a low pressure air core running longitudinally inthe center of the conduit 40. The low pressure air core draws air fromthe maintenance hole 30 above the vortex form 20 into the conduit 40.Some of the oxygen in the air core mixes with and becomes entrained inthe sewage flow, reacting with the potentially volatile dissolvedhydrogen sulfide gas (H₂S) in the liquid sewage to produce hydrogensulfate (H₂SO₄) in the solution. This reaction prevents hydrogen sulfidegas from being released into the air and then onto sewer surfaces wherecorrosion can occur or into the above ground neighborhood as a foul gas.The conduit 40 also helps to dissipate the high velocities and kineticenergy of the sewage flow by friction between the descending spiral flowand the conduit wall 45. This energy reduction through friction reducesflow turbulence and thus hydrogen sulfide gas emission from the wastewater liquid into the surrounding air. Without losing the flow'sintegrity, the gravity flow is transformed into a flow with combinedgravity and centrifugal forces.

The sewage flow completes its downward spiral near the conduit base 46,where the most intensive processes of flow mixing and aeration occur.The sewage air-flow mixture then flows out of the conduit base 46through a flow exit 50 into an energy dissipating pool 72 for furtherinternal mixing and friction. At the top surface of the energydissipating pool 72 is a generally tranquil flow that leaves themaintenance hole 30 via the effluent line 60.

As shown in FIGS. 7 and 8, other embodiments of the invention can alsobe used to mix and entrain gas in fluid flow within a conduit 120. InFIG. 7, flow is channeled through influent line 12 into separate vortexforms 102 and 112. Influent line 12 is generally a cylindrical pipe, butcan take any cross-sectional shape. Depending upon the flow accelerationdesired in the vortex forms 102 and 112, the influent line 12 and thevortex forms 102 and 112 can be oriented at a variety of slopes. Inaddition, fluid flow pumps (not shown), known in the prior art, can beutilized to accelerate the flow within the influent line 12. In FIG. 7,the influent line 12 is shown substantially horizontal.

The influent line 12 is fluidly connected to both vortex forms 102 and112. Each vortex form 102 and 112 is positioned to receive a portion ofthe flow from influent line 12 and each is generally shaped to create aspiral flow about the centerline 122 of conduit 120. Vortex form 112 ispositioned proximate to and downstream of vortex form 102. In practice,it is beneficial to direct the spiral flow of vortex form 112 in adirection opposing the spiral flow created in vortex form 102. Asdescribed in the previous embodiments, the vortex form 102 directs thefluid into a spiral of a predetermined radius (shown as R3) greater thanthe radius (shown as R7) of the conduit 120 and subsequently reduces theradius of the spiral flow (shown as R4) to be equal to or less thanradius R7 of the conduit 120 to increase the centrifugal forces actingupon the fluid. Vortex form 112 directs the flow in a similar manner,creating spiral flow of predetermined radius (shown as R5) and reducingthe radius of a that spiral flow (shown as R6).

Conduit 120 is fluidly connected to vortex forms 102 and 112 and extendsdownstream away from the vortex forms 102 and 112. The downstreamextension of conduit 120 may be oriented in any position fromsubstantially horizontal to downwardly vertical, depending upon theapplication. Conduit 120 may also extend upstream of vortex form 102.Conduit 120 includes an air intake 124 upstream of vortex form 102 thatallows air or other gases to enter into conduit 120 and mix with flowsdelivered by vortex forms 102 and 112 within conduit 120. In FIG. 7, theair intake 124 is a pipe, but could in other embodiments take any formallowing the flow of air or gases into the conduit 120 upstream ofvortex form 102. The spiral flows created by vortex forms 102 and 112create a column of air or gas that is drawn through the air intake 124and causes a portion of the air or gas to mix with and become entrainedin the fluid flow. The conduit 120 must extend far enough downstream toallow such mixing and entrainment.

The embodiment in FIG. 8 also uses vortex forms 102 and 112 to createtwo spiral flows. However, in FIG. 8, each vortex form 102 and 112receives fluid from separate influent lines 130 and 132. The influentlines 130 and 132 may deliver the same or different fluids, and thedensities of each fluid may differ. Conduit 126 is disposed withinconduit 120 about centerline 122, and receives flow from vortex form102. Conduit 126 can be formed separate from or integral with vortexform 102. Conduit 126 ends proximate to vortex form 112. Gas mixes withthe spiral flow from vortex form 102 within conduit 126. The spiral flowand gas within conduit 126 then empty into conduit 120 and mix with thespiral flow created by vortex form 112. It is again beneficial to directthe spiral flows from vortex forms 102 and 112 in opposing directions toenhance the mixing and entrainment of the gas and fluids.

This description is intended to provide specific examples of individualembodiments which clearly disclose the present invention. By way ofexample only, and without limitation, the present invention could finduse in drop structures having other than a circular or cylindricalconfiguration, thus freeing designers to construct such structuresaccording to need. This invention can also be used in non-sewerapplications where one seeks to mix gas and fluid within a conduit.Accordingly, the invention is not limited to the described embodiments,or to the use of the specific elements described therein. Allalternative modifications and variations of the present invention whichfall within the spirit and broad scope of the appended claims arecovered.

1. A method for reducing gas emissions from fluid traveling through dropstructures having a wall and a base, said method comprising: channelingthe fluid within the drop structure into through a flow channel thatforms a spiral flow of predetermined maximum outer radius andpredetermined minimum inner radius; reducing said spiral flowpredetermined maximum outer radius to increase the centrifugal forcesacting upon the fluid; and continuing said reduced radius spiral flow,with the aid of gravity, to or near the drop structure base.
 2. Themethod of claim 1, wherein the channeling of the fluid through the flowchannel includes channeling the fluid in a spirally downward slopingdirection, and wherein the method further comprising comprises:providing air access to the drop structure to allow mixing of the airwith said spiral flow.
 3. A method for entraining and mixing air oranother gas with liquid traveling within a conduit, said methodcomprising: channeling a first portion of the liquid within a firstinfluent line into a first spiral flow of first predetermined radiusaround the centerline of said conduit; channeling a second portion ofthe liquid within said first influent line into a second spiral flow ofsecond predetermined radius around said centerline of said conduitdownstream of said first spiral flow and having a rotational directionopposing said first spiral flow; reducing each of said first and secondspiral flows predetermined radii to increase the centrifugal forcesacting upon each of said spiral flows; and providing air or other gasaccess to said conduit upstream of and proximate to said first spiralflow so that the a portion of the air or other gas mixes with andbecomes entrained in said spiral flows.
 4. The method of claim 3,including a second influent line, wherein said first and second spiralflows are channeled from said first and second influent lines,respectively.
 5. The method of claim 4, wherein the said air or gasaccess is provided though a pipe centered about said centerline of saidconduit.
 6. The method of claim 4, wherein said first spiral flowpredetermined radius is reduced to a smaller radius than said secondspiral flow predetermined reduced radius.
 7. The method of claim 3,further comprising: channeling a first portion of a second liquid withina third influent line into a third spiral flow of third predeterminedradius around the centerline of said conduit and downstream of saidfirst and second spiral flows; channeling a second portion of the secondliquid within said third influent line into a fourth spiral flow offourth predetermined radius around said centerline of said conduitdownstream of said third spiral flow and having a rotational directionopposing said third spiral flow; and reducing each of said third andfourth spiral flows predetermined radii to increase the centrifugalforces acting upon each of said spiral flows; so that said third andfourth spiral flows mix with said first and second spiral flows.
 8. Themethod of claim 7, further comprising: channeling additional liquid orliquids within a one or more additional influent lines into additionalspiral flows of predetermined radii around the centerline of saidconduit and downstream of said first and second spiral flows; andreducing each of said additional spiral flows predetermined radii toincrease the centrifugal forces acting upon each of said additionalspiral flows; so that said additional spiral flows mix with said firstand second spiral flows.
 9. A method for entraining a mixing air oranother gas with liquid traveling within a conduit, said methodcomprising: channeling a first portion of the liquid within a firstinfluent line into a first spiral flow of first predetermined radiusaround the centerline of said conduit; channeling a second portion ofthe liquid within said first influent line into a second spiral flow ofsecond predetermined radius around said centerline of said conduitdownstream of said first spiral flow and having the same rotationaldirection as said first spiral flow; reducing each of said first andsecond spiral flows predetermined radii to increase the centrifugalforces acting upon each of said spiral flows; and providing air or othergas access to said conduit upstream of and proximate to said firstspiral flow so that the a portion of the air or other gas mixes with andbecomes entrained in said spiral flows.
 10. The method of claim 9,including a second influent line, wherein said first and second spiralflows are channeled from said first and second influent lines,respectively.
 11. The method of claim 10, wherein the said air or gasaccess is provided though a pipe centered about said centerline of saidconduit.
 12. The method of claim 10, wherein said first spiral flowpredetermined radius is reduced to a smaller radius than said secondspiral flow predetermined reduced radius.
 13. The method of claim 9,further comprising: channeling a first portion of a second liquid withina third influent line into a third spiral flow of third predeterminedradius around the centerline of said conduit and downstream of saidfirst and second spiral flows; channeling a second portion of the secondliquid within said third influent line into a fourth spiral flow offourth predetermined radius around said centerline of said conduitdownstream of said third spiral flow and having the same rotationaldirection as said third spiral flow; and reducing each of said third andfourth spiral flows predetermined radii to increase the centrifugalforces acting upon each of said spiral flows; so that said third andfourth spiral flows mix with said first and second spiral flows.
 14. Themethod of claim 13, further comprising: channeling additional liquid orliquids within a one or more additional influent lines into additionalspiral flows of predetermined radii around the centerline of saidconduit and downstream of said first and second spiral flows; andreducing each of said additional spiral flows predetermined radii toincrease the centrifugal forces acting upon each of said additionalspiral flows; so that said additional spiral flows mix with said firstand second spiral flows.
 15. A fluid mixer, comprising: a flow conduithaving a generally cylindrical first wall portion of a first radiuscentered around a centerline, the first wall portion having a first wallinterior surface; a first vortex form having a first flow channel ofdecreasing radius that includes a first inlet and a first outlet,wherein the first outlet is fluidly coupled with the flow conduit; asecond vortex form having a second flow channel of decreasing radiusthat includes a second inlet and a second outlet, wherein the secondoutlet is fluidly coupled with the flow conduit proximate to the firstoutlet; wherein the first and second flow channels are situated andshaped such that, in operation: fluid exiting the first flow channel isdirected into a first spiral flow traveling along the first wall portionof the flow conduit and centered around the centerline, the first spiralflow having an initial outer radius generally equal to the first radius;and fluid exiting the second flow channel is directed into a secondspiral flow centered around the centerline and having an initial outerradius that is smaller than the first radius.
 16. The fluid mixer ofclaim 15, and further comprising: a third inlet adapted to provideaccess for an additional fluid to at least one of the first and secondspiral flows.
 17. The fluid mixer of claim 16, wherein the third inletis a line having an end positioned in a center of at least one of thefirst and second spiral flows.
 18. The fluid mixer of claim 16, whereinthe fluid inlet is a line coupled with a source of air or other gas. 19.The fluid mixer of claim 15, wherein the second spiral flow has arotational direction opposing the first spiral flow.
 20. The fluid mixerof claim 15, wherein a portion of the first spiral flow and a portion ofthe second spiral flow each defines a relatively low-pressure core. 21.The fluid mixer of claim 15, wherein the flow conduit includes agenerally cylindrical second wall portion centered around the centerlineand having a second radius that is smaller than the first radius and asecond interior wall surface, wherein the second flow channel is shapedand situated such that the second spiral flow is directed to travelalong the second interior wall surface of the flow conduit.
 22. A methodfor mixing a plurality of flows in a conduit having a generallycylindrical interior wall surface centered around a centerline, andhaving an upstream end and a downstream end, the method comprising:channeling a first flow into a first spiral trajectory around acenterline of the conduit, wherein the first spiral trajectory has afirst initial radius and a first final radius that is smaller than thefirst initial radius; channeling a second flow into a second spiraltrajectory around the centerline of the conduit and proximate to thefirst spiral flow, wherein the second spiral trajectory has a secondinitial outer radius and a second final outer radius that is smallerthan the second initial outer radius; and wherein a portion of the firstspiral trajectory is situated along the interior wall surface; so thatthe first and second spiral flows mix with one another.
 23. The methodof claim 22, wherein the second spiral trajectory has a rotationaldirection opposing the first spiral trajectory.
 24. The method of claim22, wherein the second spiral trajectory has a same rotational directionas the first spiral trajectory.
 25. The method of claim 22, wherein thesecond final outer radius is smaller than the first final radius. 26.The method of claim 22, and further comprising: conveying a first fluidthrough a first influent line to become the first flow; and conveying asecond fluid that is different from the first fluid through a secondinfluent line to become the second flow.
 27. The method of claim 22, andfurther comprising: conveying a first fluid through a first influentline to become the first flow; and conveying the first fluid through asecond influent line to become the second flow.
 28. The method of claim22, wherein at least one of the first and second flows is a liquid. 29.The method of claim 22, and further comprising: providing access for athird flow to the conduit proximate to at least one of the first andsecond flows.
 30. The method of claim 29, wherein the third flow is airor a gas.
 31. The method of claim 29, wherein the access for the thirdflow is provided though a pipe centered about the centerline of theconduit.
 32. The method of claim 22, wherein the second final outerradius is of a size such that a portion of the second trajectory iscircumscribed by a portion of the first trajectory.
 33. The method ofclaim 22, and further comprising: channeling a third flow into a thirdspiral trajectory around the centreline of the conduit and proximate tothe first and second spiral flows, wherein the third spiral trajectoryhas a third initial outer radius and a third final outer radius that issmaller than the third initial outer radius.
 34. A liquid conveyancearrangement for conveying flow from an inlet at a relatively higherelevation to an outlet at a relatively lower elevation, comprising: avortex form situated proximate to the higher elevation and including achannel having an upstream end and a downstream end, wherein theupstream end of the channel is fluidly coupled with the inlet, andwherein the channel has an initial curvature and a final curvature thatis greater than the initial curvature such that, in operation, the flowpassing through the channel is accelerated and subjected to centripetalforce; a conduit fluidly connected to the downstream end of the channelof the vortex form, the conduit including a generally cylindrical wallhaving a diameter that generally corresponds to the final curvature ofthe channel, wherein the conduit is situated to carry the flow generallydownwardly from the vortex form towards the lower elevation, and whereinthe conduit includes a flow exit that is submerged relative to a levelof the flow proximate to the outlet.
 35. The liquid conveyancearrangement of claim 34, wherein the vortex form channel is generallysloped downwardly such that the flow passing through the channel isredirected along a path having an initial elevation and a finalelevation that is lower than the initial elevation.